Dashpot



Aug' 24, 1943. H. K. KouYoUlvLuA|\|l 2,327,722

' DASHPOT Original Filed March 12, 1940 BY f fa. c/

WZ ATTOR EY Patented Aug. 24, 1943 UNITED star garantir oFFlcej l,l`v2,327,722 .nasnrora i t Haroutiurn Kfliouyonmjian, Walrefield, R.'L'- 'assignor to ,Ward Leonard Electric Company,` a corporation ofNewYork j Original applicationli/Iarch 12, 191MB, Serial No.

' 323,584. Divided and this application ber 27, 19440,` Serial No.367,419

1 Claim.

This invention is particularly well adapted for use in connection withtime delay relays but is applicable to various other uses.Thisapplication is a division of my pending application Serial No.323,584, led March 12, 1940; and various disclosures herein relating tothe electromagnetic time delay relay are claimed in said pendingapplication; and are described here for the purpose of showing how theimproved dashpot functions in its cooperative action with the otherparts in this particular application of the invention.

The main object is to provide an improved dashpoi; which may be dependedupon in long continued use to function in the samemanner according tothe strength and duration of the controlling force. A further object isto avoid the use of check valves in the dashpot. Such valves arecommonly used for permittingaquick return of the piston to its initialposition but their failure to seat properly and ,uniformly at all timesaffects the controlling action to give varying and unpredictableresults. The present invention permits a rapid return of the pistonwhile avoiding Variations in the response curve that aredue to the useof check valves. Other objects and advantages will be understood fromthe following description and accompanying drawing. Q

Fig. 1 is a vertical central section showing one embodiment of theimproved dashpot applied to an electromagnetic time delay 'relay andshowing the parts in their initial lower position; Fig. 2 is a similarView showing the parts in their uppermost position, the elementcontrolled bythe relay having then been actuated; Fig.V S is ahorizontal section on the line 3 3 of Fig. 1; Fig. 4 is a horizontalsection on the line i-fi of Fig. l; and Fig. 5 is a chart indicatingchange of viscosity oi a liquid with change of temperature.

Referring to Figs. l, 2 and 3, an inverted U- shaped frame if), havinginwardly projecting 1ower ends lila, is of magnetic material, such asiron or steel. It has a central core lilo of magnetic material at itstop portion which projects downwardly to some extent within the frame. Awinding Il having a central insulating sleeve i ia is positionedbetweenA the sides of the frame l@ vand surrounds the core lb at theupper part of the Winding. A sheet metal strip 35 ofnon-magneticmaterial is secured at its ends to thelower portions of the sides of theframe lil and serves to retain the Winding l l in position.

A cylinder i2, closed at its upper endv andv of nonmagnetio material, ismovable freely within Novem- (cl. 18s-sc) l" the winding ll l and itsupper end is normally be-v low ythe lower end of the core H'lb. Thelower endof this cylinder is open and is securedn by a sealed joint tothe upper plate I3 of the dash--A pot. The cylindrical body l /1 of thedashpot is joined to its upper plate i3 by a sealed joint, the lower endlila of the` dashpot having a small central opening lil?.` The dashpotis provided with a'vertically extending projecting portion Hic at oneside having a passage Md which connects the interior top portion of thedashpot with the space Me below the `bottom plate Illa. This space isclosed by a flexible metal sheet `i5 below the plate illu, the sheet l5being united at its outer rim bya sealed joint with an extended lowerportion of the dashpot cylinder. A stem I6 carrying a head ld above theplate, Ma passes through the opening i412 with considerable clearancespace and `passes through the metal sheet i5, being secured thereto by asealed joint. The lower end of the stemvis threaded and passes freelythrough a cross-piece il, the outer ends of which are fixed to the lowerend of the dash-n pot. Above and below the cross-piece are nuts i3threaded on the stem il. It is evident that by adjusting theselnuts thestem may be adjusted vertically to any desired position and the flexiblesheet l5 will yield suiciently to permit such adjustment withoutaffecting any joint or interfere with the sealing of the unit. `Informing the sealed joints above referred to, they may be soldered,braced or otherwise formed to insure a perfectly sealed unit. Threadedconnections or joints depending upon friction are not dependable for apermanent sealing and in the above described unit, all such connectionsare eliminated, even for the purpose of adjustment. Thus there can be nochange in the unit dueto the presence of any unsealed joint.

The piston I9 of the unit, instead of being of the usual form, is a flatcircular plate of comparatively small thicknessf, This has at one sidean upwardly extending pair of spaced projections lASa which arepivotally connected by a pin Eil" tov a pair of spaced projections 2id,extending downwardly -at one side of -a platel or strip 2 i. `This plateextends partially across the interior of the dashpot. Fixed to thepiston plate I9 at the side opposite the hinged pOrtion is an upwardlyprojecting screw` bolt 22 which passes `freely through a slot 2b in `thecrossplate 2l. head'lof the boltnormally rests on the top of the plate2l and then holds-the hinged piston plate in a plane perpendicular tothe axis `of the clashpot cylinder. The lower vend of the bolt and itsnut are soldered to the plate I9 to avoid any change of adjustment. Ascrew bolt 23 is fixed to the center of the plate 2I and extendsupwardly into the lower end of a cylinder 24 of magnetic material. Theconnections of the bolt to plate 2I and to the cylinder 24 are solderedto prevent change of adjustment after the desired condition is attained.The cylinder 24 is movable freely vertically within the cylinder I2 andin its lowest normal position the top of cylinder 24 is some distancebelow the top of the cylinder I2, as shown in Fig. 1. The cylinder 24 isprovided with a Vertical slot 24a at one side to redu'ce the eiect ofinduced eddy currents when an alternating controlling current is appliedto the winding I I.

The relay may be applied to the actuation of any desired controlledelement and is here shown as serving to open a controlling circuit butcould obviously be applied to the closing of a circuit or to perform anyother desired function. A U- shaped frame 25 is shown fixed to the topof the frame IB. Passing down freely through the frame 25 and Athecenter of the core Ib is a pin 26 which projects beyond the core andapproaches close to, or may engage, the top of the cylinder I2,r asshown in Fig. l. rThe top of the pin is headed so as to be retained bythe frame 25 when the pin is in its lowest position. Pivotally mountedon the frame 25 is a latch 21, the inner end 0f which engages the top ofthe pin 26 while'its outer end is spring pressed upwardly to normallyengage and restrain a circular beveled plate 28. This plate is fixed toa shaft 29 which is supported by and longitudinally movable in theupwardly extending ends of the frame 25. A spring 30 encircles the shaftbetween the plate 2B and one end ofthe frame and tends to move the shaftto the left against the latch 21. The left-hand end of the shaft isprovided with a handle or knob 30a. The right-hand end carries aninsulated contact 3I which is connected to any desired control circuit.This contact normally engages a fixed contact 32 through which thecircuit is completed.

Returning now to the magnetic circuit of the relay, a cross-plate 33 ofmagnetic material is xed to the top plate I3 of the dashpot by thescrews 33a and normally engages the top of the inwardly projecting endslila of the magnet frame, as shown in Fig. l. This completes a magneticcircuit from the sides of the frame Ill in a main path through thecross-plate 33 and cylinder 24 to the core Illb and then to the sides ofthe frame Ill. hold the movable unit comprising the dashpot, plate 33and cylinder I2 in its lowest position with the plate 33 attracteddownwardly towards the ends Ia of the magnet frame. In order to keep themovable unit from turning on its axis and to maintain the plate 33 inalinement with the extensions I 9a under all conditions of operation, abrass plate 34 is tted slidably over the dashpot and has a recess forreceiving the side projection I4c of the dashpot, as shown in dottedlines in Fig. 3. This plate is xed by screws 34d to the under side ofthe extensions lila of the magnet.

The operation may be understood by first considering the parts in thepositions shown in Fig. 1. `When current is applied to the winding II, amagnetic ilux will be created which will `pass mainly through thecircuit, as already described, to the cross-plate 33, and the movableunit will be retained in the position shown in Fig. l. If

This magnetic circuit tends to the current is sufliciently small, noaction of the parts takes place. If, however, the current be increasedt0 or above a predetermined-amount, the magnetic cylinder 24 starts tomove upwardly at a rate of movement depending upon the strength of thecurrent in the winding II. This action is due to the magnetic attractionimposed upon the cylinder 24 by the winding tending to draw it withinthe winding. The dashpot retards the upward movement of the cylinder 24,the rate of movement being dependent upon the relation between themagnetic force exerted upon the cylinder. 24 and the retarding action ofthe dashpot. The magnetic force exerted depends, of course, upon thestrength of current in the Winding Il.

The dashpot is filled or nearly filled with a suitable liquid, such asoil, and is preferably of a character whose viscosity does not changematerially with change of temperature. When the plate of the dashpotmoves upwardly, the retarding force is dependent upon the rate of flowof the liquid through the passage I4b from the upper side of the plateI9 to its lower side. -The rate of this flo-w is adjusted, in the mannera1- ready described, by the position of the stem I6 and its head Ilia.Raising or lowering the position of the head Ia with reference to thebottom plate I4a of the dashpot will, of course, increase or decreasethe space between the plate 14a and the underside of the head IBa andthereby control the rate of ow of the liquid in the dashpot. The lowerportion of the dashpot cylinder is shown as having a slightly largerinteriordiameter I4f than the central portion .and likewise the upperportion of the dashpot cylinder is shown as having a slightly largerdiameter at Illy. The piston or plate I9 of the dashpot is tted' quiteclosely to pass along the central portion of the dashpot without muchclearance so as to reduce the passage of oil around the rim of the plateI9 to a comparatively small amount. The enlarged lower portion I4f ofthe dashpot cylinder isy for the purpose of permitting the dashpot plateI9 to be moved easily and quicklyfrom its lowest position to the portionof thecylinder having a smaller diameter. This reduces friction ofrepose of the partsand likewise avoids any tendency of the parts tostick in their lowest position and requires a comparatively light forceof short duration to raise the plate I 9 to engage the central portionof the dashpot which has the smaller diameter.A

The plate I 9 and cylinder 24 then move upwardly at a rate dependentupon the factors already described.

The magnetic attraction of the cylinder 24 is aiected by tw-o branchmagnetic circuits. One,

as already described, is through the plate 33. The other is from thesides of the frame Ill-'below the winding to the cylinder 24 and then tothe core IGZ). In theinitial position of the parts,

. the -iux passing through the plate 33 is so strong that the movableunit is held down. But as the cylinder 24 passes` upwardly, it finallyreaches a position where the flux through the plate 33 is greatlydecreased whereas the flux from below the winding to the cylinder 24 isgreatly increased. This relative change of flux in thetwo paths finallyresults in the weight'of the parts and attractive force between theplate 33 and the extensions Illa, being overcome by the 'upward pullexerted on the cylinder 24. The movable unit, comprising the plate 33,cylinder I2 and dashpot with theircontenta-then moves bodily and quicklyto their raisedy position.. as

shown in Fig. 2. 'Il'iis action raises the pin 26, trips the latch andpermits the spring 3B to open the controlling circuit at the contacts 3land 32. At the time this action takes place, the plate I8 of the dashpotpasses into the region of the larger diameter I4g which suddenly reducesthe retarding dashpot action and thereby cooperates in permitting aquick movement of v the unit in its nal responsive action. i

Upon discontinuance of the current in the winding II, or its reductionto a sucient amount, the weight of the parts will restore then to theirinitial position shown in Fig. l. The controlling switch may be reclosedby the handle 30a and the device is then in a condition to repeat itsaction. i

The cylinder or movable core 24 when released is permitted to fallrapidly within the cylinder I2. This is due to the fact that when theplunger starts to move down, the liquid in the dashpot will turn theplate I9 about its pivot pin 20 and cause its opposite portion to moveup against the plate 2l, Thispermits the free ow of the liquid aroundthe edges of the plate I9 in its tilted position, and thereby permitsthe plate I8 and parts connected therewith to fall to their lowestposition shown in Fig, 1. It is evident that when the attractive forceagain raises the cylinder 24, the plate I9 will always have the samedefinite position in relation to the other parts and always giveuniformity of action in its upward movement. It is thus apparent thatthe variables introduced by the use of check valves are avoided and thatthe device permits a quick return of the parts to their initialpositions. i

It is evident that the relay cannot function to give immediate responseto an excessively high current in the winding Il because the core orcylinder 2 4 must always travel upwardly a certain distance within thecylinder I2 before there is sufcient change of flux in the respectivemagnetic paths to permit the upward movement of the movable unit.`Moreover, the relay is dependable for securing the same response curvewith reference to time intervals and the strength and duration ofcurrent in the winding I I because there are no variables which affectthe operation, even after long continued use.

The parts may be variously designed and modified for adaptability toparticular requirements and in accordance with the preferences of thedesigner. In some cases the strip 35 may be made `of magnetic materialand reduced in size or extent provided the magnetic circuit is designedto insure a proper ux at the bottom of the winding il to overcome. atthe proper time, the magnetic attraction of the magnetic circuit whichinitially retains the movable unit in its lower position. 'I'he core Ibmay sometimes be eliminated or may be extended further within thewinding I I for adaptation to the proportions of other parts.

Where the temperature changes of the dashpot are such as to materiallyaffect the viscosity yright-angle sides of the opening 43.

The viscosity rapidly decreases `with initial increases in temperature;and decreases much less with 4continued increase in temperature. rlhecompensation for such changes should correspond with the viscosity curveof the particular liquid used.

,In the drawing, as more particularly shown in Fig. 4, an opening 43 ofgeneral right-angle tri angle form is made in the plate or piston I9having the hypotenuse corresponding in general with the shape of theviscosity curve of the particular liquid used, after rstdetermining theviscosity curve of the liquid used. Means is then provided for makingthis opening more or less effective in accordance with the temperatureof the liquid. At low temperatures the opening is fully uncovered and asthe temperature increases the opening is more extensively closed withthe initial increases in temperature than with the higher increases intemperature, in accordance with the viscosity curve of the liquid used.For accomplishing this change of the opening, a curved bij-metallicstrip 44 is mounted edgewise on the `plate I9, being attached at one endto a post 45 fixed to the plate. The other end of the strip carries aplate 46 resting on the piston plate I9, one side of the plate beingparallel to one of the This side is adapted to slide over the opening 43in a direction at right-angles to the said right-angle side of theopening and close it more or less. Upon increase of temperature, thestrip 44 will move the plate 46 outwardly to an amount correspondingwith the increase in temperature and upon decrease of temperature willwithdraw the plate 46. Thus the position of the plate will corresspondwith the temperature of the dashpot. But owingto the fact that the shapeof the opening 43 is of general triangular form and that the sidethereof nearest the plate 46 is at right-angles to the direction ofmovement of the plate 46, the opening will be closed to a greater extentupon temperature increases starting at low tempera tures than upon thesame temperature increases starting at higher temperatures.` Thus theextent of the opening is made to conform in general with the change ofviscosity of the liquid and automatic compensation therefor is obtained.

Although a preferred embodiment of the invention has Vbeen described, itwill be understood that various modifications maybe made withoutdeparting from the scope of the invention and of the liquid used in thedashpot` and thereby lay, special means isl provided for compensatingfor the change in viscosity. Fig. 5 indicates in a general way thechange in viscosity of a liquid, such as some oils, with changes oftemperature.

' materially affect the timing` of action of the reg that the dashpotmay be used for various purposes.

I claim:

A dashpot comprising an enclosing cylindrical body portion, a pistonwithin said body portion, a movable element for raising the piston fromits normal lowest position to an upper position, said piston being inthe form of a plate and having a pivotal connection with said element,and means connecting said piston and said element for restraining andholding the piston in a plane at right-angles to the axis of the bodyportion in the normal lowest position of the piston and during anyupward movement of the piston and for permitting free movement of thepiston on its pivot -to a position inclined to the axis of the bodyportion during downward movement of the piston.

HAROUTIUM K. KOUYOUMJIAN.

